User Review: M51 Direct Digital DAC - Professional-grade sound

[This review replaces my earlier one. It includes those comments and adds my impressions from a week's worth of listening to the M51.] INITIAL IMPRESSIONS Set-up was easy. Beautifully made. Volume control is sweet. From the first notes a sense of professional-grade reproduction and control. Obvious increase in dynamic range. High frequency rendering the best I've heard on my system, especially so with hi-res material. Gorgeously delicate. Sibilants fully and tightly resolved. Stage has moved further back beyond front wall. Greater competence on complex dynamics, with each voice and instrument handled with seemingly independent ease. More believably at Symphony Hall on my Pops favorites. No strain on anything so far. An impression of almost no coloration. Nothing around any sound source but silent emptiness. Characteristic bass fatness of tubes now leaner, more like solid state. Gratefully handing control to M51.

AFTER A FEW DAYS Past few days stealing time to listen to a level of reproduction way beyond anything in my previous experience. I can only describe this technology as revolutionary in what it offers to us in the home. It's like I'm on a space voyage -- stunning, astonishing, scary. Part of me says NAD doesn't even know what they've created. Some issues playing files. Seems the unit gets confused when changing to files at a different sampling rate. In touch with NAD support and the guy I spoke to said he can't help with "this new digital stuff" -- suggests I "go higher in the organization" for assistance. These are, I think, teething pains. If Amarra put me in the studio, the M51 places me in its duplicates in all parallel universes. I am overwhelmed to the point of not going to work just to submerge in the out-of-body experience the M51 affords.

AFTER A WEEK I'm drawn to confirmation. You may recall in Jon Mark Hancock's comments on M51 the urge to turn it up and up. I am rewarded tonight with Yes songs, always among the biggest of sounds. I find it truly remarkable that at volumes with 100 dB+ peaks, there is not a little strain, muddying, and loss of articulation... there is NONE! What I've just written is impossible but it is happening right now and it has been sustained. And I'm not doing this to stress-test the system but to more fully enjoy the music. Because I can. The signal purity from M51 appears to be all but absolute, unloading amplification of anything spurious.

I'd call the M51 luggable. It's 17 inches wide, 11 inches deep and 3 inches high. It weighs over 12 pounds. The two front panel buttons have marvelous look and feel. The display can be read from across the room: input (eg, USB), sampling rate in, and volume (if enabled) in dB. The remote volume control is sweet, allowing you to raise and lower in 1 dB increments, and perfectly repeatable for a given setting of preamp volume (if you use a preamp). Can't tell if it's cumulative or per use break-in/warm-up, but the sound is noticeably improved after about an hour (I'm allowing for the familiar effects of warm-up of my tubed units.) This is when the space voyage reliably begins. My high-volume experience last night tells me that, for all these many years, despite fussing with cables, power, and components, there's been a lot of non-musical information in the signal. When amplified along with desired content, there's contention between signal and noise and a loss of presentation clarity. I believe the M51 outputs signal quality of professional gear (and with the highest S/N Stereophile has ever measured -- on M2). After last night's 6-hour, all-classical session I know that M51 is the best thing to happen to me since becoming an audiophile. The experience is other-worldly. I will again invoke the metaphor of a space voyage: 3, 2, 1, guidance is internal... We have lift-off of Mission Fifty-one! System: iMac / Amarra 2.3 / iTunes / NAD M51 / ARC SP-14 / ARC D-150 / Fulton J-Modular speakers (M51 replaced Cambridge Audio DacMagic with Pangea P-100 power supply)